Day 07计算属性computed的使用
2019-03-15 本文已影响0人
忆曦雪_
-
computed 和methods的区别
我们可以使用 methods 来替代 computed，效果上两个都是一样的，但是 computed 是基于它的依赖缓存，只有相关依赖发生改变时才会重新取值。而使用 methods ，在重新渲染的时候，函数总会重新调用执行。使用 computed 性能会更好，但是如果你不希望缓存，可以使用 methods 属性。 - 购物车练习
注意:适应手机端要加一行代码：
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">
完整代码：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title> computed购物车练习</title>
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<!-- 通过CDN引入Vue.js -->
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
<style type="text/css">
.container {
display: flex;
flex-direction: column;
font-family: 黑体;
width: 98%;
margin: 0 auto;
}
.title {
font-size: 25px;
}
.title1 {
font-size: 30px;
}
.item {
display: flex;
border: 1px solid darkgrey;
border-radius: 10px;
width: 95%;
height: 80px;
margin-bottom: 10px;
align-items: center;
/* 垂直方向居中 */
justify-content: center;
/* 水平方向居中 */
padding-left: 10px;
padding-right: 10px;
}
.item-id {
flex: 1 1 7%;
}
.item-name {
flex: 1 1 20%;
}
.item-intro {
flex: 1 1 15%;
}
.item-price {
flex: 1 1 15%;
}
.item-intro {
flex: 1 1 15%;
}
.count {
display: flex;
flex: 1 1 35%
}
.goods-count {
width: 15px;
}
.item-img img {
width: 100%;
height: 100%;
}
.butt {
width: 100px;
height: 40px;
color: white;
border-radius: 10px;
font-size: 15px;
background-color: orangered;
border: 1px solid darkgrey;
outline: none;
font-family: 黑体;
}
.butt:hover {
background-color: lightsalmon;
}
a {
color: black;
text-decoration: underline;
}
.card {
display: flex;
justify-content: space-between;
align-items: center;
}
</style>
</head>
<body>
<!-- Vue-app的根容器 -->
<div id="app">
<div class="container">
<span class="title1"><img src="img/applelogo.jpg" />Apple官方旗舰店</span><br>
<span class="title">商品列表</span><br>
<div class="item" v-for="goods in goods">
<div class="item-id">
{{goods.id}}
</div>
<div class="item-name">
{{goods.name}}
</div>
<div class="item-img">
<img :src="goods.img">
</div>
<div class="item-intro">
<a :href="goods.intro">详情</a>
</div>
<div class="item-price">
¥{{goods.price}}
</div>
<div class="count">
<span>购买:</span>
<button type="button" @click="goods.count-=1" :disabled="goods.count===0">-</button>
<input type="text" class="goods-count" v-model="goods.count" />
<button type="button" @click="goods.count+=1">+</button>
</div>
</div>
<hr>
<div class="card">
<h3>您所选取商品总价：￥{{totalprice}}</h3>
<button type="button" class="butt" @click="totalCount()">立即结算</button>
</div>
<div class="result" v-if="show">
您购买 {{totalCount}}件商品,需要支付总价为：{{totalprice}}元。
</div>
</div>
</div>
<script type="text/javascript">
var app = new Vue({
el: '#app',
data: {
goods: [{
id: 1,
name: 'iPhone8',
price: 3999,
count: 1,
img: 'img/ipone8.jpg',
intro: 'https://item.jd.com/5089267.html'
}, {
id: 2,
name: 'iPhoneX',
price: 6349,
count: 1,
img: 'img/iponeX.jpg',
intro: 'https://item.jd.com/5089253.html'
},
{
id: 3,
name: 'iPhoneXS ',
price: 8258,
count: 1,
img: 'img/iponeXS-Max.jpg',
intro: 'https://item.jd.com/32960766754.html?extension_id=eyJhZCI6IjE3NTUiLCJjaCI6IjIiLCJza3UiOiIzMjk2MDc2Njc1NCIsInRzIjoiMTU1MjQ1MTk5NiIsInVuaXFpZCI6IntcImNsaWNrX2lkXCI6XCJjYTJiMWJhMS1iNDBhLTQyNGYtOGQ0NC1mNjUxYWQ5NzdiYjJcIixcIm1hdGVyaWFsX2lkXCI6XCI4MTUzNTc1NDA4Nzg2NjczNjI5XCIsXCJwb3NfaWRcIjpcIjE3NTVcIixcInNpZFwiOlwiYjNjMTJlMWMtYTk3Mi00MjAxLTg4NzMtYzI0ODNjZDFiZDI3XCJ9In0=&jd_pop=ca2b1ba1-b40a-424f-8d44-f651ad977bb2&abt=0'
},
{
id: 4,
name: 'iPhoneXR',
price: 5288,
count: 1,
img: 'img/iponexr.jpg',
intro: 'https://item.jd.com/32962088967.html?extension_id=eyJhZCI6IjE3NTUiLCJjaCI6IjIiLCJza3UiOiIzMjk2MjA4ODk2NyIsInRzIjoiMTU1MjQ1MTgwOSIsInVuaXFpZCI6IntcImNsaWNrX2lkXCI6XCI0NzZlZWYwYi1lYzdmLTRiOGEtYTE0MS03MjBjMTNjZjI3YzBcIixcIm1hdGVyaWFsX2lkXCI6XCI4NTg2MzMyNzExNzgzMjA2MTk2XCIsXCJwb3NfaWRcIjpcIjE3NTVcIixcInNpZFwiOlwiYjNjMTJlMWMtYTk3Mi00MjAxLTg4NzMtYzI0ODNjZDFiZDI3XCJ9In0=&jd_pop=476eef0b-ec7f-4b8a-a141-720c13cf27c0&abt=0'
}
],
show: false
},
methods: {},
computed: {
totalprice: function() {
var totalprice = 0;
for (var i = 0; i < this.goods.length; i++) {
totalprice += this.goods[i].price * this.goods[i].count;
}
return totalprice;
},
totalCount: function() {
alert('恭喜您，购买成功！')
this.show = true;
var totalCount = 0;
var len = this.goods.length;
for (var i = 0; i < len; i++) {
totalCount += this.goods[i].count;
}
return totalCount;
}
}
})
</script>
</body>
</html>
运行图演示：
购物车演示.gif
- 搜索练习
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>computed练习搜索页面</title>
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">
<style type="text/css">
.container {
width: 90%;
margin: 0 auto;
}
.input-box {
width: 50%;
height: 30px;
margin-bottom: 10px;
}
.item {
display: flex;
height: 100px;
border: 1px solid #eee;
border-radius: 8px;
margin-bottom: 8px;
}
.item-title {
flex: 1 1 80%;
}
a{
color: black;
text-decoration: none;
}
a:hover{
text-decoration: underline;
}
.item-thumbnail {
flex: 1 1 20%
}
.item-thumbnail img {
width: 100%;
height: 100%;
}
</style>
</head>
<body>
<div id="app">
<div class="container">
<input type="text" v-model="searchString" placeholder="请输入您要搜索的内容..." class="input-box" />
<div class="item" v-for="article in filteredArticles">
<a :href="article.url" class="item-title">
{{article.title}}
</a>
<div class="item-thumbnail">
<img :src="article.image">
</div>
</div>
</div>
</div>
<script type="text/javascript">
var app = new Vue({
el: '#app',
data: {
searchString: "",
// 数据模型
articles: [{
"title": "堪称神器的3款在线工具，你一定用得上！",
"url": "https://www.jianshu.com/p/e83e7999346b",
"image": "https://img.haomeiwen.com/i11438996/56b25f32c9307b4b?imageMogr2/auto-orient/strip%7CimageView2/2/w/640/format/webp"
},
{
"title": "经典面试题：从 URL 输入到页面展现到底发生什么？",
"url": "https://www.jianshu.com/p/45ba3e0d0c7e",
"image": "https://img.haomeiwen.com/i3973862/d90954249a6f6ccd.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1000/format/webp"
},
{
"title": "如何免翻墙使用谷歌搜索和Chrome应用商店",
"url": "https://www.jianshu.com/p/484f8e6c88f6",
"image": "https://img.haomeiwen.com/i858154/015a4b083685a3d1.jpg?imageMogr2/auto-orient/strip%7CimageView2/2/w/800/format/webp"
},
{
"title": "四款前所未有好用的黑科技APP，绝对的良心实用，赶紧告诉家人",
"url": "https://www.jianshu.com/p/2aec84d269fe",
"image": "https://img.haomeiwen.com/i16042993/168b2cb17fd7ec0c?imageMogr2/auto-orient/strip%7CimageView2/2/w/640/format/webp"
},
{
"title": "坚持学英语的方法有哪些",
"url": "https://www.jianshu.com/p/0a6a61b0933c",
"image": "https://img.haomeiwen.com/i3525704/c7293758fc59e56b.jpg?imageMogr2/auto-orient/strip%7CimageView2/2/w/960/format/webp"
}
]
},
computed: {
// 计算函数，匹配搜索
filteredArticles: function() {
var articles_array = this.articles,
searchString = this.searchString;
//搜索关键词为空,则返回原始数据集
if (!searchString) {
return articles_array;
}
//搜索关键词去除无用空格,转换为小写
searchString = searchString.trim().toLowerCase();
//过滤数组中每个元素,如果
articles_array = articles_array.filter(function(item) {
if (item.title.toLowerCase().indexOf(searchString) !== -1) {
return item;
}
})
// 返回转化后的数组
return articles_array;
}
}
})
</script>
</body>
</html>
运行演示：
演示
